The present invention concerns an energy converter comprising a boiler, a turbine, a condenser, a feed pump and a generator and, if needed, a recuperator and a pre-feeding pump, in said energy converter the thermal energy to be supplied to the boiler having been arranged to maintain a cyclic process driving the generator and thereby to produce electricity, and in said energy converter the turbine, generator and feed pump having a joint rotor.
Ample quantities of high-grade waste heat are released by industry and by ships, such as flue gases and hot process gases. The energy contained in these cannot often be utilized directly as heat energy, among other things because of great transport distances and/or surplus supply of heat energy at the site producing the waste energy. It is for his reason that particularly in the U.S.A. and in the U.K., where there is little district heating activity, development work has been started on an energy converter for converting this waste heat into electricity. It is based on the conventional power plant process wherein an organic liquid is used as circulating fluid instead of water. The existing state of art will become apparent e.g. by reference to: Giglioli, G. et al: Tetrachloro-ethylene Rankine cycle for waste heat recovery from ceramic tunnel kilns, SAE/P-78/75, 1978 and to U.S. Pat. Nos. 3,061,733 and 2,961,550.
The planned and constructed experimental plants are however usually based on conventional power plant technology, in other words, they comprise an impulse turbine, speed changing gears, slip ring seals, a lubrication system, a vacuum pump, etc. This implies that they require maintenance, their efficiency is low and they are expensive. In hermetic designs (in the U.S. patents cited above) liquid-lubricated bearings have been employed, which at the very high speeds of rotation involved wear out relatively fast and also require a special pipe system to convey the lubricating liquid of the present invention is to achieve an improvement in these energy converters of prior art. A more detailed object of the invention is to provide an energy converter the Rankine process of which is totally enclosed, thereby obviating seals and vacuum pumps, and wherein the bearing arrangement has been carried out with virtually wear-free gas bearings (with continuous service life more than 100,000 hrs), of which the radial bearings function with the ambient process fluid vapour, and that for turbine and feed pump are used inexpensive single-stage radial machines in which the lower surface of the turbine rotor constitutes one abutment face of a gas thrust bearing. In this manner the converter has been rendered maintenance-free and, moreover, low in price owing to its simplicity. Furthermore, the minimal friction of a gas bearing, compared with liquid-lubricated ones, improves the efficiency of the turbo-generator. The other objectives of the invention and the advantages gained by it will be apparent in the disclosure of the invention.
The objectives of the invention are attained by means of an energy converter which is mainly characterized in that the shaft has been rotatably carried with gas-dynamic bearings using the vapour of the circulating fluid, and that the lower surface of the turbine rotor has been disposed to serve as one abutment face of a gas-static thrust bearing.
The energy converter of the invention may be provided with valves, and the condenser placed at a suitable elevation so that the apparatus is able to start on thermal power alone.